Abstract
Tamoxifen is an anti-oestrogenic drug which is widely used in the treatment of patients with breast cancer. There is increasing interest in using the drug both for benign breat disease and as a chemo-preventative agent of the drug in women at high risk of breast cancer. Despite the fact that the acute side-effects of the drug are few, its agonistic and antagonistic oestrogenic effects are not fully known and may have some undesirable effects for patients treated with the drug for several years. A number of studies carried out recently indicate a varying degree of change in bone mineral content following treatment with tamoxifen. These studies concentrated mainly on bone mineral density measurements only and non of them reported the effects of tamoxifen on lean body mass and fat mass. In this study we measured lean body mass and fat mass in tamoxifen-treated females and a comparison group to determine the difference between the two groups.
Twenty-six women receiving tamoxifen (20 mg/d) have participated in this study. The control group comprised 31 healthy women of a similar age. Total body bone mineral (TBBM) was measured using a dual-energy X-ray absorptiometry (DXA) (Hologic INV., Waltham, U.S.A.). Similarly, regional and total body soft tissue (lean and fat tissue) were measured using the DXA system. In addition to DXA measurements, percentage body fat (%BF) was measured using total body potassium counting (TBK), skinfold anthropometry (SF), infrared interactance (IR) and bioelectric impedance analysis (BIA).
Results from DXA alone showed that there were no significant differences between the two groups for TBBM, regional and total body lean tissue mass. However, there was a significant difference between the two groups (
P<0.05) for %BF measurement. Similarly there was a significant difference between the two groups (
P<0.05) for %BF measured by other body composition techniques. Although there is no other research reported on the effects of tamoxifen on %BF, this retrospective study indicates that tamoxifen may lead to increase in fact content in women who are subjected to this treatment.
We conclude that this observation is probably related to the agonistic oestrogenic effect of Tamoxifen on body fat. To our knowledge this deleterious effect has not been reported before and it should be taken into considerable when comprising different types of anti-oestrogenic drugs. Furthermore, patients should be warned about this side-effect when they are prescribed Tamoxifen therapy.